This invention relates to a control waveform generator for an electronic musical instrument, which utilizes charging and discharging of a capacitor.
A control waveform generator, often called an envelope waveform generator, is used for an electronic musical instrument for varying with time the tonal elements such as pitch, color and volume of a musical tone produced by the musical instrument. A control waveform generated by the control waveform generator is usually applied to a voltage control type variable filter which controls the tone color and to a voltage control type variable gain amplifier which controls the tone volume. The characteristics of the control waveform generator are controlled for varying with time the color and volume of the musical tone produced.
Among the control waveform generators of the type referred to above is one type in which the control waveform is generated by using charging and discharging of a capacitor, and another type wherein a memory device stores a desired control waveform. For example, the former is disclosed in U.S. Pat. No. 3,897,709 to Hiyoshi et. al. dated Aug. 5, 1975 and the latter is disclosed in U.S. Pat. No. 4,109,208 to Tomisawa et. al. dated Aug. 22, 1978.